The corrosion cell. It works just like a battery works.
A corrosion cell requires four key elements.
a. A cathode, or negatively charged particle.
b. An anode, or positively charged particle.
c. An electrical path.
d. An electrolyte, usually water
When all four elements are present, electron flow begins. Electrons flow from the anode through the electrolyte into the cathode, through the electrical path and back to the anode, completing...
2. Unprotected Steel
This is a real world example of unprotected steel. Mild steel has 3 of the 4 elements needed for a corrosion cell built in. It has anodic and cathodic particles that are touching creating an electrical path. All that is missing is an electrolyte, water. Once water is present, electrons begin flowing from the anode into the electrolyte, then into the cathode, and through the electrical path back to the anode. As this...